Purification of gases



Patented June 24, 1930 "UNITED STATES ATENT oF F lcE ALPHONS O. JAEGER, OF CHICAGO, ILLINOIS, AND JOHA NN BERTSOH, 01 ST. LOUIS, HISSOURI; SAID J'AEG-ER ASSIGNOR TO THEBELD'EN COMPANY, OF PITTSBURGH,

PENNSYLVANIA, A. CORPORATION OF DELAWARE 11o Drawing.

This invention relates to the purification of gases and more particularly to the purification of gases which are to be used in the catalytic reactions.

6 Volatile compounds of the metalloids, sulfur, phosphorus, arsenic, antimony, selenium and tellurium, frequently actas catalyst poisons in varlous vapor phase catalytic reactions. Sulfur compounds are especially 10 harmful in reduction or hydrogenation 16'.

actions and are also undesirable in many catalytic oxidations in the vapor phase. I

The present invention has for 1ts ob ect the removal of volatile'metalloid compounds and particularly volatile sulfur compounds from pounds yieldin halogens with or without the aid of physica agencies such as heat, light,-

, particularly ultraviolet light, silent electric action of halogen with metalloid compounds, and chemical catalysts, such as metals, oxides, and salts, and particularly halides of iron, .'coppe'r, aluminum, antimony, tin, gold, titanium, zirconium, uranium, vanadium, bismuth, molybdenum, zinc, manganese, chromium, nickel, cobalt, silicon, and the like.

Purely "surface catalysts, such as, coke, wood charcoal, bone'charcoal, artificial charand such combined catalysts are particularly.

. effective as the lar e surface of the surface catalysts" greatly on ance the efficiency of the metal compounds;

discharge and pressure which aid in the recoal, activated carbon, finely divided silicic' rumrrcn'rron or GASES Application filed August 28, 1925. Serial No. 5 3,204.

It is an advantage'of the present invention that substantially all of the volatile metalloid compounds and particularly volatile sulfur compounds, bothinorganic and organic,'can

be transformed into compounds which are readilyremoved from the gas stream and the whole purification may take place in a single manufacturing operation. The invention, however, is not limited to the removal of all of the metalloid compounds by treatment with halogen, and, on the contrary, particularly where large amounts .of hydrogen sulfide are present, part or all of theh drogen sulfide may be removed by the we known desulfurizing processes, such as treatment with iron ox de and the like, andthe remain 1 mg gas may then be treated with halo en accordingto the present invention. Ot er particular metalloid compounds may be removed beforetreatment with halogen and thls is of advantage. in the case of. certain gases which contain finely dividedvmetalloid compounds in the form of dust which maybe. removed by various precipitation and wash-' ing methods before treating the gas with; 5 halogen. In general, the present invention is applicable to practically all gases containing volatile or gas borne metalloid com-,

pounds and the process of this invention may be applied as the only treatment or in com bination with other known methods-Actremovi particular compounds. WZ liave found thatthe treatmentiwi'th halogen is effective in transforming'volatile' metalloid compounds into compounds orproducts which can readily be removed fromthe gas stream. In the case of many com-' 5 pounds, and particularly organic compounds of sulfur, the action is largely'a halogenating A action transformin the compounds into more or less h'alogenate products which, for the most part, are less volatile thanthe original compounds. In many cases, however, metal-' loid' compounds, and particularly hydrogen sulfide and similar compounds, are oxidized and, in some cases, the action may be a com- -bined halogenating and oxidizing one. vIn

the case of some metalloid compoundsflve are. not sure and have been unable to determine precisely what chemical reactlon goes on and we do not wish to limit our invention to any particular chemical reaction and, on the contrary, the invention is broadly directed to the removal of volatile or gas formed metalloid compounds from gases by treatment with halogens. We also do not wish to limit our invention to the production of compounds of lower volatility by treatment with halogen since, in some cases, notably in the cases ofsome sulfur compounds, products may be produced which may be actually more volatile than the original compounds but which may also 'be more readily soluble in solvents or absorbablein absorbents and can thus be removed from the gas stream. In many cases a combination of the two effects is noticed an the products of the halogenating treatment may both higher boiling and more readily absorbed or dissolved. Thetreatment with halogen may also render some of the metalloid products acid by oxidation and thus permits the removal of the compounds by treatment with bases or basic compounds.

The above described effects are some of those which we have noted in the case of particular metalloid substances when treated by our process but the invention is in no sense limited to any of the reactions mentioned above or to any combination of these reactions which are given merely as probable explanations of'some efiects of our process and are not intended to the invention in any way. a

The treatment with halogen may be effected in different ways. Thus, we may use free halo ens in the vapor base or in solution, solutions of halogen yielding substances such as hypochlorites and hypobromites, and similar compounds. We may also use gaseous compoundsv which yield halogen and which may, at the same time, yield oxygen such as nitrosylchloride, and the like.

Heat, pressure, illumination with ultraviolet light and silent electric discharge may be used alone or in combination with chemical catalysts either simultaneousl or rogressively or partly simultaneously and partly progressively.

Thecatalysts may be in the form of solids, mounted on solid masses over which the gases are passed or may be in the form of a rain of finely divided catalysts falling through the gases in the same direction as the gas flow or incounter-current thereto. Catalysts may also be in solution or suspension in liquids and, in some cases, the

halogenating agents may be present in the same solution. Gaseous catalysts, such as phosgene, nitrosylchloride, sulfurchloride or b romide, iodine vapors, sulfur dioxide, or trioxide or various combinations of these gases may also be used either as the sole catalysts or in combination with solid catalysts.

When gaseous halogen is used in the presence of gases which tend to react therewith with explosive violence, it is frequently necessary to dilute the halogen with inert gases, such as nitrogen, steam, and the like. We have found that steam is particularly suitable as a diluting agent both on account of its inertness and its relatively highspecific heat which tends to prevent local overheating.

In gases containing metalloid compounds which are relatively inactive with halogen, the presence of a gas or gases which are halogenated very readily, may be effective in inducing the reaction between the relatively inactive compounds and halogen, probably due to the large amounts of heat evolved by the reaction of the readily halogenated gases with part of the halogen.

When dissolved halogen or halogen yielding compounds are used, for example, when chlorine or bromine water or solutions of hypochlorites or hypobromites contact between the halogen and the gases to be treated may be rendered more effective by increasing the surface of contact by means of percolating towers or by atomizing the solution into the gas stream. The liquid may berecirculated through the towers. or atomizingchambers with suitable enrichments of halogen or halogen compounds to make up for 'the losses in reactions with gas. Catalysts in solution or in solid suspension maybe present in the halogenating liquid and the baflles or tower fillings may advantageously be of catalytically active materials. Heat, increased pressure, or both, are frequently desirable and illumination of the interior of the scrubbing towers with ultraviolet lamps, or silent electric discharge, may be also advantageously used, in order to increase the effectiveness of the halogenating liquid. The various physical accelerating agents may be applied simultaneously or progressively in any desired combination.

Evolution of halogen, in the nascent state, 7 can be effected by treatment of a solution containing halogen compounds with chemicals which set free halogen, for. example, oxidation agents. The gases may be passed through the halogen generator, either contacting with the surface of the liquid or bubbling through it or in any other suitable manner, in order to bring the halogen evolved rapidly into contact with a maximum amount of gas. Electrolytic halogen may also be used and the gases permitted to pass over the halogen pole of an electrolytic cell. A par-' ticularly advantageousmethod is to use a perforated hollow electrode as the halogen pole and pass the gases to be treated through the hollow electrode, permitting them to escape through perforations into intimate contact into the halogen evolved. As the evolution of halogen can be accurately controlled by controlling the current through the cell, a very easy and accurate halogenation .control can be achieved in this manner.

in described.

Other and further variations in themethod of halogenating the gases will be apparent to those skilled in the art and are includedwithin the scope of the present invention.1:"The foregoing enumeration of various methods and combinations of methods and the detailed description in specific examples, which will follow below, are to be taken as illustrations of the invention and 'in no sense dothey limit the invention to the particular methods, combination of methods or apparatus therebe free dot the dioxide, and the like, in various Ways'.' 1T he gases may be scrubbed withlvarious'scrub-t bing liquids such as water,'c'a'ustic-solutions,

solutions of carbonates, or organic solvents,

- such as high boiling oils, products of th di tillation ofv coal tar, petroleum distillates,' x tetralin, cyclohexane, cyclohexanon, andthe' like. Combinations of these solvents, either in the form-of mixtures or by progressive use of different solvents,'may alsobe employed and are advantageous in some cases; 1:

Pressure, with or without-cooling, 'isal'so.

effective and may advantageouslybe used many cases to improve the solution or absorption by reducing the partial pressure oftheyj v :Avery effective method cons sts-in increasing the strength of the catalystjin thedirecltionofgas flow; Other and different 'varlar 1- tionsf may be used" and will befapparent to matu ed: w halogenated metalloid products, may .generated in various ways, for example, by distillation at: atmospheric pressure, or under 1 a vacuum, precipitation bychemicalsand other means." Where absorbents are-lu'sed', v

solvent vapors. v e

The halogenated products may also be re,

moved by absorption or adsorption in various solid bodies of high porosity'or capillarity,

such as charcoal, coke, bone charcoal, .acti vated carbon, and similar carbonaeous mate. I

rials. Highly porous silicious materialsare also veryefiective, particularly porous s'ilicic acid, such as silica gel, and they maybekused either alone or in combination with the aboye mentioned carbonaceous materials.

A further method of removinghalogenated products consists in freezing then outby lowering the temperature and increasing the pressure to the point where the production precipitates in the form of liquids or solids.-

This method is particularly advantageous and applicable to large scale operations as itpermits the recovery of the halogenated metalloid compounds in the form of by products' which are frequently'of considerablecommercial importance. For example, ;halogenated sulfur compounds are usefulasjvulcanizing agents or as solvents and thelvalue" of the recovered ,metalloids often is more gressi'vely, or partly simultaneously and.

partly progressively, may be employed and,

in many cases, is very desirable. For .example, where a-relatively high boiling halothat when the-gases are passeduo er -the -jab the prodncts vabsorbed such as, forex'am pay fol-the costs of purifyf.

genated metalloid" compound is-Ifor'med,

"which has.commercial valueyit' may be re! productswhich may- 9' then be removed by was 'charcoalsor carbons or-siliciousmaterials,

impregnated withhalogenationi'catalysts', so;

sorbent, the catalysts'bring' abouti'halogen'a-f areabsorbed, thus 'performing'ithB-gt ea tion andatthesame tlme theproduct's formed wo vfuncadvantage ,that *halogenation nd,1 1abs'o'rp tionftake place in a singleconta ero'riicham;

which may be strongly heated'jfloallygby' the halogenation reaction. ,Overh those'lskilled in the art.

Solvents, which have her and very high gas speeds withcorre'spond-h 7 Zing efliciency may be used. Afurtherj-fad'vantage lies in the fact thatthe relatively large 7 v masses of absorbents tend to; cool the gases 1 1,

.. g is h e a by avoided and the life of the, atalysts, as ';well as the efliciency ofithe process, may be; f v a I greatly increased. The catalystimpregnated absorbents may also be: arrauged iu-z ne 5" through with .air, preferably at an" elevated temperature or by washing with solvents for inorganic or organic solvents or sulefur,

compounds orfor carbon tetrachloride: or

ogen sulfur compounds, or 'ot-hermetalloid 'n halogen derivatives of various. hydrocarbons,

both alifatic or aromatic, "which .may. be formed in small amounts when the gases to be purified contain hydrocarbons, -Wa-sh1ng solutions may be .hot orcold water .or; d1l ute alkalies and solutions containing emulslfylng agents or detergents may also be employed. Blowing with steam or heating in a vacuum is also'efioctive in many cases. The various methods of regeneration may be used singly or in combination, simultaneously orprogressively The'products removed during the: j

regeneration in many Cases y b re o red '1 and-utilized commercially.

' and covers the use of halogen in any suitable amounts for the purpose of removing n 1etal loid compounds from gases.

The sizeof the halogenating apparatus,

I absorbers, or washers, depends in large 15- measure on the'nature of the gas and the nature of the metalloid compounds present therein. The gas speed is also variable and, in general, should be as fast mean he used consistent with a sufiiciently thorough removal of the metalloid compounds so that the p'urified gas is sufiiciently pure for the purposes for which it is intended. In the case of the removal of sulfur compounds, an analysis for sulfur in the gases, before and after passing through the halogenation and absorption apparatus, is the most reliable method of determining whether the process is operating satisfactorily. A similar analysis may also be used in the case of other metalloids to determine the effectiveness of the process.

It should be clearly understood that the present invention is not limited to a complete removal of all of the metalloid compounds present in any particular gas. On the con-' trary, in many cases, it is sufiicient to completely remove some of the metalloid compounds only or to remove all of the metalloid compounds above a certain percentage. The criterion is to be found in the use for which the gas is intended and it is in general unnecessary to purify a gas to a greater degree of purity than is demanded by the uses to which the gas is to be put. The present invention can be used to remove almost quantitatively certain metalloid compounds and to substantially completely remove others but it is equally applicable to gases where a complete removal of some or all. of the metalloidcompounds is notneccssary and in some cases is undesirable.

The invention will be described more particularly in the following specific examples which are illustrations of the applicationof the principles of the present invention to particular gases using particular modifications of the invention. It should be clearly understood, however. that the invention is not limited to use with the gases enumerated ini-the'specific examples, nor. tothe particular-, letails of procedure therein set forth, since theexamplcs are merely illustrations of the invention and are in no sense to be considered as limitations.

Eat-ample 1 Nitrogen contaminated with traces of sulfur compounds such as carbon disulfide and carbonyl sulfide is thoroughly mixed with about of chlorine gas. The mixture is then slowly passed through an apparatus Nitrogen containing hydrogen sulfide and traces of. .carbon disulfide is compressed 1O atmospheres and passed through a vessel having a chlorine proof lining and provided with trays containing bleaching powder. The effluentgas may advantageously be brought into contact with a chlorine carrier such as aluminum or'iron in order to.com'plete the reaction which is frequently not completed in the bleaching powder chamber especially where the gas speed is high. The gas, which is still under a pressure of 10"atmospheres, is washed with a caustic soda solution and is then practically free from sulfur.

lt'awmple 5 Crude illuminating gas which may contain hydrogen sulfide and organic sulfur compounds is passed through a scrubbing tower where it is brought into contact with chlorine water trickling down through the tower. The chlorine water is constantly circulated and the losses of chlorine are replaced by additional' chlorine gases before the water enters the tower. Bromine water can also be used instead of chlorine water. The gases coming from the scrubbing tower are then passed through a tower filled with activated carbon which may be impregnated either partially or wholly with copper phosphate. In large units, the absorption chamher is cooled by copper coils through which cooling water flows. The gases are then passed through washing towers where they are washed first with water and then with caustic soda. The gas, after washing, is praetically free from sulfur if the number of purifying units has been suitably chosen inf connection with the amount of sulfur impurities in the gas.

The activated carbon becomes charged with reaction compounds and can be regenerated by blowing through steam which removes the halogenated products absorbed in the carbon and these products may be renated with iron e or. manganese chlois mixed with a smal fide is mixed with a s" tivated carbon. 7

covered. In thecasegnzffordinary crudeil- I luminating gas,- 'chloriire-sulfurv compounds are vformed and some jcases alsochlorine derivatives of methaneggethylene and. benzol.

The chlorine products recovered may be com-- washed witha solution aifso ium bicarbom pr highpurity; v

passed throng er: filled with achon: my argu be partly or wholly impregnated iron chl'o ride or manganesechl' 'mers. A mercury ya in catalytic is practicallyfi'ee from sulfur-.-

, ri de'iwhichact ascar -.l a'mp isajrranged so solution of final product of pii ty i g m -i taming small amountsdfot'g anic'sulfur com; 0 P u s s-t fi w lh q f mfwh r which carries dissolved coppe'ii gcl loridelor suspended manganese oxide in o der'tojjncrease its efiectiveness." 'rhe gas-m" be washed with, a diluted solution 1 o a hypochlorite. Thetreatment with zshlorine water or hypochlorite solution -iriay'.' ja xlinriita'geousl take place in a 'towerfwhere the so utions v trickle. overj af su V, order to expose a" greater surface to the gas. After passing throughithechlorinating tower, the gas is towers containmg absorbent carbon and i;i s-- finally. washed" with a caustic soda,solution. Then the gas w imzile 17 a.

a 7 Crude commercial, water which contams, among othersg-Tliydrogen sulfide and or- Y ganic sulfur'compounds; -:as impurities, is

' passed through a percolatin'g tower lined with acid-resistant stone or quartzplates and .filled with flint orfother l siliceous pebbles.

Chlorine water containing copper chloride used in the tower and is {continuously recirculated, the chlorinedost 'bemg madeup by the addition of fresh. the water before -it enters the to The water gas then passes through xja unt: of chlorine gas:

ution containing 0 water followed by washing with' an alkaline solution.-

gas is then compre'ssed to 200 atmospheres and water removed in a suit- 1 I abletower whereupon the gas, still under high pressure,- is passed through the two absorption towers lined with copper and provided with, layers of a filling prepared as follows:

parts of water glass (40 B.) are (ii luted' with 1000 parts ofwater, and 150 parts of carbonized sugar are stirred in and an;

ammoniacal copper carbonate solution containing 5 partsof copper added.

with "vigorous agitation until the [mixture rejI-Iydrochloric. acid is then: added gradually [acts neutral litmus and thefwhole solidifies in -,the form of a gel. The gelis pressed and the formed into granules with 'dextriniat-a somes After is then practically free from (loal colating tower with chlorine water and'then I washed-with ,a-sodilun bicarbonate solution. v

wholly-impregnated with aluminum phos- The gasis'thenheatedin a heat exchanger, n V a mixed withgsteam' in excess; and passedg-a through 'a catalytic chamber-at [500 (3., the; g chamber beingfilled with ironoxide contact masses The carbon monoxide and steam is converted into carbon dioxide and hydrogen 7 in the known way. The gas is then-cooled precipitate'repeatedly washed at room teme .peratur'e,the washing being kept u until- I Water soluble salts are no longer note linthefiltrate. "The doughy substanceis dried and Z .185 what, elevated temperature and is thenr acti V; vated by heating to 400-500 (1.1 in a stream;v V of ammonia followed by blowing; with nitro- 1 containing 4.5% CO ,"38%.. CO, j s 54.5% H5, 1% CH; and 2%'N and also containing about 250 grs. of IOU-clung, Y the sulfur in the form-of inorganic or: f organic sulfur'co'mpounds istreated in LP I 7 'The.washed*gasfis then 'passedrinto a tower] filled with1charcoalwhi0hmaybe partly'oor phate.-' Ther'eupomtheJgas sP SSed through a asecond tower filled with absorbent carbon p 7' produced by 'charrin'gxsubstances richin antially inert filling inh' and washed with water under pressure to remove carbon dioxideand aftenreleasing the pressure, the washed gas is again treated in V V acid-resistant percolating towers ,which' are free from'liron by means of ahypochloritesolution which reacts with the last traces offisulfur compounds. Tov-removethetransfor- I mation products, vthe gas is first washed with 4 V water and then passed through an absorptiontower filled in the manner to thatdescribed in'Example -7, 'A further vash'with 'am'moniacal copper oxide solution follows and hydrogen produced is, of high purity and cellently 'suitedfor catalytic purposes: 4

' constitutes a simple and effective method of Ewample .9

Hydrogen, produced by the reaction of commercial zinc and commercial hydrochloric acid, and which contains considerable amounts of arsenic compounds, is passed through chlorine orbromine water and is first washed with cold water and then with caustic soda solution. The hydrogen so purified is practicallyfree from arsenic. The arsenic compound may be recovered by the wash liquors.

'It will be seen that the present invention purifying gases which contain metalloids or metalloid compounds and is applicable to a wide range of gases, such as those produced by the distillation of coal or carbonaceous materials, such as wood, gas from coke, gases resulting from the cracking of hydrocarbons under pressure, various types of water gases, and gases produced by chemical reactions.

The process may also be applied to gases indirectly produced from coal, as by the Messerschmidt process, and to the gasses produced by the Linde process from air or by various electrolytic processes.

A further important field consists in various natural gases and tail gases from the distillation of petroleum and other similar materials. Exhaust gases which have been subjected to chemical treatment and have become contaminated during the treatment may also be treated by the present process.

In the claims, the word substance is used to cover chemical elements, their oxides, salts, both simple and complex, and other compounds, and the word compound is limited to the combination of at least two chemical elements into a single chemical individual. The expression active halogen as used in the claims is intended to be limited to chlorine and bromine and excluded iodin which is not active in most of the purification processes of the present invention.

We claim:

l. A method of purifying gases containing metalloid substances and hydrogen orhydrocarbon gases which comprises treating the gases with active halogen in the presence of a halogen carrier and removing the reaction products of active halogen and the metalloid substances to a substantial extent.

2. The method of purifying gases containing sulfur substances and hydrogen or hydrocarbon gases which comprises treating the gases with gaseous chlorine, removing the reaction products of the chlorine and sulfur substances to a substantial extent.

3. The method of purifying gases containing metalloid substances which comprises treating the gases with halogen and removing at least part of the reaction products of halo gen and the metalloid substancesby. chilling the treated gases.

4. A method of purifying gases containing metalloid substances which comprises treaty ing the gases with active halogen and removing part at least of the reaction products of the halogen and metalloid substances by means of a high boiling organic solvent.

5. The method of purifying gases containing sulfur substances which comprises treating the gases with halogen and removing at least part of the reaction products of halogen and the sulfur substances by means of tetralin. a

6. The method of purifying gases containing metalloid substances which comprises treating the gases with halogen and removing at least part of the reaction products of halogen and the metalloid substances by means of solvents followed by chilling.

v 7 The method of purifying gases containing metalloid substances and hydrogen or hydrocarbon gases which comprlses treating the gases with halogen and removing at least part of the reaction products of halogen and the metalloid substances by means of solvents followed by treatment with solid absorbents.

8. The method of purifying gases containing metalloid substances .and hydrogen or hydrocarbon gases which comprises treating the gases with halogen in the presence of a combined halogen carrier and a solid absorbent.

treating the 'ases with halogen in the presence of a com ined halogen carrierand solid absorbent followed by treatment with a solvent for the reaction products of halogen-with the metalloid substances.

11. The method of purifying gases containing sulfur substances which comprises treating the gases with halogen in the presence of a combined halogen carrier and solid absorbent followed by treatment with a solvent for the reaction products of halogen with the sulfur substances,

12. A method of purifying gases containing mixtures of hydrogen, carbon monoxide and sulfur substances which comprises treating the gases with small amounts of gaseous active halogen and removing the reaction products of the halogen and the sulfur substances to a substantial extent.

13. A method of purifying containing metalloid substances which comprises 9. The method of purifying gases containtreating the gases with active chlorine and removing part at least of the reaction products of the chlorine and metalloid substances by means of a high boiling organic solvent.

Signed at St. Louis, Missouri, this 24th day of August, 1925.

ALPHONS O. JAEGER. J OHANN A; BERTSGH. 

